The present disclosure relates to a sheet feeding device which feeds a sheet on which an image is to be formed and an image forming apparatus including the sheet feeding device.
An image forming apparatus is provided with a sheet feeding device which feeds sheets stacked on a sheet feeding cartridge to an image forming part by a pickup roller. The pickup roller is disposed above the sheet feeding cartridge and is configured to abut against a front end portion of the uppermost sheet and feed the sheets from the uppermost sheet. In order for the pickup roller to abut against the uppermost sheet even if the amount of the stacked sheets decreases, there is known a sheet feeding device provided with a lifting plate on which the sheets are stacked. The lifting plate is configured to be inclined upward around its upstream side end in the conveying direction.
In such a sheet feeding device, an inclination angle of the lifting plate varies dependent on the amount of the stacked sheets on the lifting plate. For example, in a case where the sheets are fully stacked, the lifting plate hardly inclines; in the case of a last sheet, the inclination angle increases.
On the other hand, the sheet feeding cartridge is provided with an end cursor which abut against a rear edge of the sheets to restrain a length direction of the sheets. As shown in FIG. 7, the end cursor 101 is provided slidably in the conveying direction in an upright standing posture with respect to a bottom plate 102a of the sheet feeding cartridge 102 so as to be adjusted to the size of the sheets.
However, if the end cursor 101 is always in the upright standing posture with respect to the bottom plate 102a of the sheet feeding cartridge 102, in a case where the amount of the stacked sheets decreases and then the lifting plate 103 is inclined, a distance L1 along an upper surface of the lifting plate 103 between a downstream side surface 101a of the end cursor 101 in the conveying direction and an abutment position P of the pickup roller with the uppermost sheet becomes longer in comparison with the corresponding distance L2 in a case where the lifting plate 103 is not inclined. Thus, as indicated by the solid line of FIG. 7, if the sheets S are fully stacked, the pickup roller abuts against the uppermost sheet S1 at a suitable abutment position P. However, if the lifting plate 103 is inclined, as indicated by the double-dotted chain line of FIG. 7, a sheet S2 stacked on the lifting plate 103 shifts backward on the lifting plate 103 by a distance d toward the end cursor 101 side, that is, toward the upstream side in the conveying direction. Then, the downstream side end of the sheet S2 in the conveying direction does not reach the suitable abutment position P with the pickup roller.
Thus, if the downstream side end of the sheet in the conveying direction does not reach the suitable abutment position P with pickup roller, a failure, such as an overlapped feeding of the sheet, may easily occur. This failure occurs significantly for a small size sheet, a high rigid sheet such as a card, a high smoothness sheet or the like. Also, since the abutment position of the pickup roller and the sheet varies depending on when the sheets are fully stacked or when a small amount of sheets is stacked, even if a sheet can be fed normally, there may occur a problem such that the sheet feeding interval increase and thus an image is not formed at an suitable position on the sheet.
Accordingly, in order to solve such a problem, there is a sheet feeding device provided with the end cursor having an arc-shaped part at a lower end portion on a sheet side surface. In the sheet feeding device, even if an inclination angle of the lifting plate varies, the rear edge of the sheet abuts against the arc-shaped part so as to be pushed toward the upstream side in the conveying direction.
However, in this sheet feeding device, since the rear edge of the sheet may not abut against the arc-shaped part depending on the rigidity of the sheet and the stacking condition of the sheets, it is not impossible to shift the sheet to the suitable abutment position with the pickup roller surely. Therefore, a stable sheet feeding performance which does not cause a conveying fault, such as the overlapped feeding, cannot be obtained even if the amount of stacked sheets decreases.